Fuse attachment for electric plugs



Dec. 28, 1948. A.- LA RIZZA FUSE ATTACHMENT FOR ELECTRIC PLUGS 2Sheets-$heet 1 Filed Aug. 9, 1947 FIG.4

F 5 INVENI'OR. KWTHONY LoRIZZA Dec. 28, 1948. I LA RIZZA 2,457,477

FUSE ATTACHMENT FOR ELECTRIC PLUGS Filed 'Aug. 9, 1947, 2 Sheets- Sheet2 an SH INVENTOR. 1 1 ANTHONY LoRlZZA BY FIG. 9 dsnm ffil f ATTORNEYSPatented Dec. 28, 1948 (UNITEDSTATES PATENT OFFICE Anthony La Rizza,Revere, Mass.

Application August 9, 1947, Serial No. 767,671

provide a fuse attachment which can be mounted on one of the prongs ofan ordinary electric plug thereby converting it intov a fused plug.

.Fused electric plugs are now commonly made with the fuse element builtinto the plug. With this construction if the fuse blows or melts, theplug becomes useless and must be replaced by another. plug.

With= my invention the fuse element can be applied to a prong of anyordinary plug, and if in use the'fuse-gives away, the fuse element maybe removed from the prong of the plug and a fresh fuse element appliedthereto. In other words, with inyinvention the blowing of the fuse doesnot render the plug itself inoperative, because in order to repair thedamage, it is only necessary to remove the blown fuse element from theprong of the plug and replace it by a fresh fuse element.

"Moreover, my invention has the further advantagethat any ordinary plugcan be converted into a fusedplug by merely mounting the fuse attachmenton the prong of the plug, and if at any time the plug is tobe used undercircumstances in which afu'se is not required, such fuse attachment canbe demounted from the prong of the plug.

I In'order to give an understanding of the invention, 'I haveillustrated in the drawings some selected embodiments thereof which willnow be described after which the novel features will be pointed out inthe appended claims.

In the drawings:

Fig. 1 is an enlarged view of an electric plug Fig. 7 is-a view similarto Fig. l but showing a Q differentembodiment of the invention. 7

Fig. 8 is a View of one of the retaining strips. Fig. 9 is a section onthe line 99, Fig. .7. .Fig. 10 isa section on the line l0.l0, Fig. 7.

1115 an enlarged fragmentary sectional.

6 Claims. (01. 200f115-5) View showing a portion of the insulating stripand thefuse element.

Fig. 12 is a fragmentary sectional view showing a still differentembodiment of the invention.

R-eferring first to the embodiment of the invention shown in Figs. 1 to6, I indicates an ordinary electric plug provided with the prongs 2 and3 and connected to the cord 4 leading to the appliance to which the plugis connected. These parts may be such as are usually found in electricplugs and constitute no part of my present invention, which, as statedabove, is a fuse attachment adapted to be removably mounted on one ofthe prongs of the plug.

The fuse attachment shown in Figs. 1 to 6 comprises a retaining member 5of insulating material which is provided with two openings 6 and 1 toreceive the prongs 2 and 3 of the plug I. The attachment also comprisesan insulating strip 8 made of paper or some other suitable insulatingmaterial which is provided at one end with a head portion 9. Theinsulating strip is assembled with the retaining member 5 by placing thehead portion-9 beneath one end ID of the retaining member 5 andthreading the strip 8 through the opening 6 'to form a loop ll adaptedto embrace one of the prongs of the plug I, said strip 8 extendingunderneath the retaining member 5 and then being threaded through thetwo slots l2 with which the retaining member is provided as shown at l3in Fig. 1.

The fuse attachment also includes a fuse element in the form of a stripM of conducting material which is provided at one end with a headportion l5. This fuse element l4 embraces the loop portion of theinsulating strip 8 andthe head end of the fuse element extendsthrough-the opening 6. The head l5 thereof underlies the retainingmember 5 and is confined between the latter and the insulating strip 8.

The other end of the fuse element I4 also extends through the opening 6of the retaining member, and then extends around the head 9 oftheinsulating strip as shown at I6, the end 3 can be easily applied to anyelectric plug l by placing the retaining member over the prongs of theplug and introducing one of the prongs into the loop ll of theinsulating member 8.

When the device is thus applied to the plug, the portion of the fuseelement l4 which embraces the prong 2 is insulated therefrom by theinsulating strip 8, but the end portion I! of the fuse element which islocated inside of the loop of insulating material will contact with theprong 2.

When the plug thus equipped with a fuse attachment is plugged into asocket connection, the portion of the fuse element which embraces theprong 2 will contact with the complemental contact elements of thesocket connection and a circuit will be established through the fuseelement inasmuch as the end thereof is contacting with the prong 2.

If, during use, abnormal current conditions arise which might injure theappliance to which the plug is attached, such abnormal currentconditions will melt the fuse at the place IQ of reduced cross sectionalarea thereby breaking the circuit and preventing injury to theappliance.

The blowing of the fuse does not in any way effect the structure of theplug itself, for the plug with the blown fuse may be removed from thesocket element and the fuse attachment removed from the plug andreplaced by an attachment having a fresh fuse, thereby again putting theplug into condition for use.

In the construction shown in Figs. 1 to 6 the fusing point IQ of thefuse element is more or less exposed, and there is a possibility thatwhen the fuse blows, the accompanying flash may blow out of the socketto which the plug I is connected.

In the embodiment shown in Figs. 9 to 12, I have shown a construction inwhich the fusing point of the fuse element is enclosed in a sealedcasing, thus eliminating any possible danger from a flash occasioned bythe blowing of the fuse.

In the form of the invention shown in Figs. 9 to 11, indicates the plughaving the usual prongs 2 and 3 and 4 indicates the cord connecting theplug to the appliance.

The fuse attachment illustrated in Fig, 9 is provided with two retainingmembers 2|, 22 of insulating material which are spaced slightly fromeach other and are connected at their ends in any suitable way, as bymeans of cement 23. Each strip is provided with two openings 24, 25 toreceive the prongs 2 and 3 of the plug, and each strip is also providedwith an additional somewhat larger opening 25, the purpose of which willbe presently described.

The fuse attachment shown in Fig. 9 also involves a strip 28 ofinsulating material similar to the strip 8 shown in Figs. 1 to 6. Oneend 29' of this strip is located between the two retaining members 2|,22 and said strip of insulating material is bent into a loop 30 whichextends through the alined openings 25 of the retaining members 2|, 22and is of suflicient proportions to receive and embrace the prong 2 ofthe plug I. Thestrip 28 also has a portion 3| extending between thetworetaining members 2 22, the end 32 of which. is bent downwardlythrough the alined openings 26 of the retaining members as clearly seenin Fig. 9.

The fuse element is indicated at 34 and it is provided with a loopportion 35 that embracesithe loop 30 of the insulating strip, one end 36of the fuse element is confined between the retaining members 22, 23 andoverlies the end portion 29, of the retaining strip. Another portion310i the fuse element is also confined between the retaining members 2|,22 and overlies the portion 3| of the insulating strip. The fuse elementis also provided with a loop portion 38 which embraces the down-turnedportion 32 of the insulating strip and said fuse element further has aportion 39 located between the two retaining members 2 I, 22 andunderlying the portion 3| of the insulating strip,.the end portion 40 ofthe fuse element being located between one leg of the loop 30 of theinsulating strip and the prong 2 and having contact with said prong.

The fusing portion or the portion of the insulating strip of reducedcross sectional area where the fuse element will melt is shown at 42 andis located in the loop portion 38 of the insulating strip which embracesthe down-turned leg 32 of insulating material.

The loop portion 38 of the fuse element which contains the fusing point42 is enclosed in a sealed casing 43. Thiscasing may comprise acylindrical shell of insulating material; the lower end of whichisclosed by a cap member 44. In the combstruction: shown in Fig; 9 thecap 44 has a still: 45 anchored thereto which extends. through theshell' 43 and which has at its upper end a head 46 that engages theupper side of the top retaining member 2|. and which also closes andseals, the opening 26 in the retaining member.

The shell 43 is held tightl clamped against; the underside of the lowerretaining member and by means of this construction, the loop portion 38of the fuse element is located within a. sealed container.

The device shown in Figs. 7 to 11 operates in the same way as that shownin Figs. 1 to 6. The fuse attachment comprising the two retainingmem'aers 2| 22, the insulating strip 30, the fuse element 34, and thesealed casing 43 constitute i a unitary structure which can be readilyapplied A plug having. this to the plug I, the. fuse element will melt.at the point 42 thereby breaking the circuit to the appliance. With thedevice shown in Figs. 7 toll. any flash Which. might occur by theblowing of the fuse is contained entirely within the sealed. casing 43.

The fact that the fuse attachment is separate from the plug but can bereadily mounted thereon makes it possible to convert any ordinaryelectric plug into a fused plug by simply mounting my improved fuseattachment on one of the prongs thereof The fuse attachment has thefurther advantage that it is relatively simple in construction and canbe inexpensively manufactured.

Instead of using cement for uniting the retaining members 2|, 22, I maysimply staple said members together as shown in Fig. 12 wherethey areconnected by a staple element 50, the legs 5| of which extend throughboth retaining members and are bent or clinched over as shown at 52.

I claim:

1. The combination with an electric plug having prongs for insertioninto a socket terof' a fuse attachment. therefore comprising a strip ofinsulating material adapted to embrace the sides and end of one of saidprongs, and a fuse element embracing the insulating strip and providedwith a fusible portion, one end of the fuse element being locatedbetween said insulating strip and said prong and in contact with thelatter, said insulating strip insulating the remaining portion of saidfuse element from said prong.

2. The combination with an electric plug having prongs for insertioninto a socket element, of a fuse attachment for said plug comprising astrip of insulating material presenting a U-shaped formation to fit overone of said prongs, a fuse element embracing said U-shaped strip ofinsulating material, an end portion of the fuse element being bentaround the end of the strip of insulating material and located on theinside of the U-shaped formation and in contact with said prong, themain portion of said fuse element being insulated from the prong.

3. The combination with an electric plug having a pair of prongs forinsertion into a socket terminal element, of a fuse attachment thereforcomprising a retainer member of insulating material having openings toreceive said prongs, a strip of insulating material anchored at one endto said retainer and adapted to embrace one of said prongs, a fuseelement in the form of a strip embracing the strip of insulatingmaterial and thus situated to contact the terminals of a socket elementwhen the plug is plugged thereinto, one end of the fuse element beinglocated between the insulating strip and the prong which it embraces andin contact with said plug, said 1-? having prongs for insertion into asocket terminal element, of a fuse attachment for said plug comprising astrip of insulating material adapted to embrace the sides and end of oneof said prongs, a fuse element having a portion embracing the insulatingstrip and thus situated to contact the terminals of a socket elementwhen the plug is plugged thereinto, one end of the fuse element beinglocated between the insulating strip and the prong of the plug which itembraces, said fuse element having a fusible portion between said endthereof and the part which contacts with the socket element, and asealed enclosure enclosing the fusible portion of the fuse element.

5. The combination with an electric plug having prongs for insertioninto a socket terminal element, of a fuse attachment therefor comprisinga two-part retainer member of insulating material having openings toreceive said prongs, a strip of insulating material anchored at one endof said retainer and having a portion received between the two parts ofthe retainer and also having a loop portion which projects through anopening in one part of the retainer and embraces one of the said prongsand further having a laterally extended end portion, a fuse element inthe form of a strip having a loop portion which embraces the loopportion of the insulating material and is thus situated to contact theterminals of a socket element when the plug is plugged thereinto, saidfuse element having another portion embracing the laterally extendingend portion of the insulating strip and provided with a fusible portion,the remaining portion of said fuse element being situated partly betweenthe two parts of the retainer member and partly between one leg of saidloop of insulating material and the corresponding prong of the plug,with which prong said fuse element has contact and a sealed casingenclosing the fusible portion of the fuse element.

6. The combination with an electric plug having prongs for insertioninto a socket terminal element, of a fuse attachment therefor comprisinga strip of insulating material having a portion which embraces one ofsaid prongs, and a fuse element embracing said insulating strip andhaving one end interposed between the insulating strip and the prong andin contact with the latter, said insulating strip insulating theremaining portion of the fusible element from said prong.

ANTHONY LA RIZZA.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 332,286 Pfannkuche Dec. 15, 18851,664,408 Frakes Apr. 3, 1928 FOREIGN PATENTS Number Country Date345,199 Great Britain Mar. 12, 1931 Certificate of Correction Patent No.2,457,477. December 28, 1948.

ANTHONY LA RIZZA It is hereby certified that errors appear in theprinted specification of the above numbered patent requiring correctionas follows:

t Column 4, line 75, claim 1, for therefore reed therefor; column 5,line 35, claim 3, for the Word plug reed prong,- column 6, line 7, claim5, for end of read and to;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 3rd day of May, A. D. 1949.

THOMAS F. MURPHY,

Assistant Gammz'ssioner of Patents.

Certificate of Correction Patent No. 2,457,477. December 28, 1948.

ANTHONY LA RIZZA It is hereby certified that errors appear in theprinted specification of the above numbered patent requiring correctionas follows:

Column 4, line 7 5, claim 1, for therefore read therefor; column 5, line35, claim 3, for the Word plug read prong; column 6, line 7, claim 5,for end of read end to;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 3rd day of May, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommz'ssz'oner of Patents.

